Atmospheric aerosol is a mixture system composed of gases and particles having a certain stability and sedimentation velocity in the gravity field, also is a liquid or solid particulate system suspended in the atmosphere with a diameter of 0.001-100 μm, which is one of complex and harmful pollutants in the atmosphere environment. In terms of atmosphere energy balance, aerosols take effect on radiation transmission within a very wide range from ultraviolet, visible to infrared wavebands. The aerosphere layer where aerosols exist is heated under the optical effect of aerosols, so that the solar radiation reaching the ground surface is reduced to affect ground evaporation and water cycle as well, which is named as the direct effect of aerosols. Also, aerosols have the action of cloud condensation nuclei, a large amount of aerosol particles may cause the increase of number density of cloud droplets and leads to the decrease of mean radius of cloud droplets and reduction of rainfall and cloud amount, so that the radiation characteristics of cloud are changed, which is named as the indirect effect of aerosols. Because of the foregoing, the energy balance of ground-atmosphere system is changed, so that the conditions of climatic environment required for the survival of human beings are affected. Therefore, the researches about the direct and indirect effects of aerosols become the basic issue in atmosphere science.
At present, in the atmospheric sounding field in China, the routine observation of optical parameters of aerosols (such as scattering phase function and light absorption) has not been reported, the scientific observation at academic level of scattering and absorption characteristics of aerosols is still in progress, the synchronous and integrated measurement of all optical characteristics of aerosols (aerosol scattering coefficient, absorption coefficient, scattering phase function, extinction coefficient, transmittance, visibility and single scattering albedo) has not succeed, and there is a lack of scientific instruments for direct measurement of aerosol scattering phase function and single scattering albedo of aerosols. During the measurement of scattering coefficient and absorption coefficient of an aerosol through the known cavity ring-down spectroscopy, the aerosol absorption coefficient is determined by measuring the extinction coefficient and scattering coefficient. This method is indirect for the measurement of aerosol absorption coefficient, and fails to provide the direct measurement result of aerosol scattering phase function. Also, the presently-used scattering coefficient measurement lacks of the direct measurement result of light scattering intensity at paraxial narrow angle (e.g. integral turbidity measurement), which results in the large error of aerosol scattering coefficient measurement because of the lack of paraxial forward/backward scattering measurement.